Only members of opposing realms may attack each other; the Open RvR server still focuses on Order versus Destruction.

Unfortunately, its not a free for all I was looking forward to a truly open pvp system, but alas it is not so.
Sooo, it appears the only major upside to Open RvR is more pvp areas (also more griefing) and no lvl buffs (some scenerios and quests allow for lvl's to be temp buffed up to the min req for that area).

The chicken effect is still in Open RvR atm I believe (as someone mentioned on the official forums),
so if someone 2 tiers higher lvl then the area attacks you they still get the debuff (and funny chicken animation).

From the mainsite:
This Wednesday we are going to clone some of our busiest servers to help spread the load around and to reduce queuing times. Please note however that this is not a solution for a server where only one side has queues; it will only be used when the entire server is too full to avoid issues with the population balance. The servers that we will be cloning are as follows:

Karak Eight Peaks will be cloned to Tor Anroc
Karak Azgal will be cloned to Zhufbar
Karak Hirn will be cloned to Yvresse
Eltharion will be cloned to Tiranoc

Here is a quick explanation of how this process works:
When we clone a server, we copy all the information of that server all character data, guild data, zone information etc and copy it to a new server. This means that if you had a character on the original server, you will have the exact same character on the new server as well - he will have the same name, the same gear, the same items in his backpack and the same guild information. You can then choose, along with your friends whether you want to carry on playing on your original server or if you'd prefer to move across and play the version on the new server instead. Whichever you decide, the other copy of your character will remain so that if you change your mind later, it will be easy to move across.

Here is a quick example to illustrate the process. Let's say you have a level 25 Witch Hunter called Jorgen. He's in a guild called Malleus Maleficarum and he's Renown Rank 20. After the cloning process, there will be two identical copies of Jorgen, one will be on the original server that you chose when starting the game while the other will be on the new server. If you choose to play on the new server then you simply carry on where you left off with your level 25 Witch Hunter, if your friends join you then your entire guild remains intact and you can all carry on fighting together the only difference is that this time there are no queues to log in! If you carry on adventuring with Jorgen on the new server then the 'original' Jorgen will still be on the first server at level 25, renown rank 20 etc the two versions do not both advance at the same time.

This system makes it easy to move servers but it is very important that you and your friends all discuss which of the two servers you will play on, this way your guild or alliance won't get split up and you can carry on playing together.

Chuck Norris beat Halo 2 on Legendary using only the strafe buttons and flashlight -.-